PLATE 14 



EXPLANATION OF FIGURES 



62 A transverse section through the optic region of a nine-day embryo which 

 at the four-cell stage was treated with a solution of 50 cc. sea-water, to which 

 had been added 15 cc. m/12 butyric acid. The yolk-sac is devoid of vascular 

 tissue. The space in the optic cup (on the left side of the figure) normally occu- 

 pied by a lens, contains a blood lacuna. On the right side is seen the attach- 

 ment of the upper optic stalk and the base of the lower. 



63 Transverse section of the same embryo from which figure 62 is taken; it 

 is a section passing through the optic anlagen, showing isolated crytrocytes, 

 solid heart, and unusual eye-formation. 



ABBREVIATIONS 



Bl.L, blood lacuna Myc, myocardium 



Endc, endocardium Oc, optic stalk 



Erth., erythrocytes O.st., optic stalk 



Ht., heart Y.s., yolk sac 

 L., lens 



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